Well mine seems to be reconnecting to wifi after I (slide to) unlock - not used it long enough to see if it disconnects after x time of use tho...
But it is definitely slower;
See the difference between the top two speed test, performed after upgrading to 4.2.1, and the rest, that were on 4.0.1 (I never bothered with the 4.1 OS)
However, it does seem to have fixed the auto-send for email tho - prior to this update, any email sent from within an app, such as sending a photo from the Photos app, would just sit in my outbox untill I opened the Mail app, went to Outbox, tapped to open the mail and tapped send - which was a pain! With this update, it now autosends...
Just hope I don't get the problems with it disconnecting or refusing to connect over wifi! Maybe a quick fix will be out with 4.2.2 to re-speed up the wifi?